Sections of fluid conduit must be connected together, or to other fittings in a conduit network to carry gases and liquids without leaking from the network. The fluid pressure varies from low pressure lines, such as sewage lines where the pressure is essentially atmospheric pressure, to higher pressure water lines and the like, up to very high pressure industrial lines where the pressure is 10,000 pounds per square inch (psi) or more.
Conventional conduit connections are made using a gasket that is essentially clamped and squeezed between hollow members attached to each conduit. The clamping force is exerted by bolts in a typical flange connection, by a threaded configuration on a typical pipe union, and like apparatuses.
For example in a typical flange connection, conventional gaskets are made from a material that is softer than the flange material, typically metal, plastic, rubber, or the like. Sealing of the connection is accomplished by clamping the flanges very tightly together so that the gasket is squashed between the two flanges. Typically the clamping force is provided by several bolts through corresponding holes around the flanges. To ensure proper sealing the bolts must be tightened evenly to a high torque. The flanges must be strong enough to resist distortion under the clamping forces, and as a result such flanges are commonly heavy, costly, and cumbersome, especially for high pressure conduits.
Similarly in a pipe union the threaded members are tightened to squeeze the sealing faces. In some unions of this type a gasket is used between the faces, while in others no gasket is present and the metal faces alone provide the seal when squeezed together.
Conduit networks can comprise a large number of connections. Significant longitudinal forces are exerted on the conduits when the conventional connections are tightened to exert the required clamping force. These forces are transferred through the conduit network from each such connection, causing stress on the entire network. The network must be designed to accommodate these forces, and careful installation is required to avoid excessive stress and resulting failure of components.
A prior art conduit coupling disclosed in U.S. Pat. No. 2,491,004 to Graham uses the pressure inside the conduit to force a gasket into engagement with a housing to seal a pipe coupling.
In some applications it is desired to have one conduit section or fitting swivel or rotate with respect to the next. It is known to use springs in such applications to urge a stationary seal against another rotating seal with sufficient force to prevent leakage between the two. Such swivel couplings are disclosed for example in U.S. Pat. No. 2,927,805 to Faccou, and 3,057,646 to Brumagin.